In a backlight module, light emitting diodes (LEDs) employ a reflection-light mode. A reflecting cavity is formed between Printed Circuit Board (PCB) surface of LEDs, reflecting surface, and a light guide panel (LGP). As shown in FIG. 1, light emitted by LEDs is reflected into the LGP via the reflecting surface, and light is fully mixed after passing through the reflecting cavity, thereby decreasing the phenomenon of hot spots. The reflecting surface can be arranged on a middle frame, or formed by bending a backplane. Because the inner structure of the backlight module is compact, heat is mainly dissipated by heat conduction, and the PCB of an LED lightbar is flatly stuck on the backplane, thereby enlarging contact surface for conducting heat away. Because the reflecting cavity is enclosed in a compact structure, the heat flow of air cannot be conducted, thus it is difficult to form effective heat convection.